PhD opportunities

[PROVIDED] - Finite element models for the study of hydrogen embrittlement of steel structures

Thesis proposal

Area of expertiseMechanics
Doctoral SchoolISMME - Systems Engineering, Materials, Mechanics, Energy
SupervisorM. Jacques BESSON
Research unitCentre of materials
Contact
http://www.mat.mines-paristech.fr/Accueil/Propositions-de-theses/
Starting dateOctober 1st 2021
KeywordsFinite element method , Hydrogen embrittlement , Steel structures
AbstractThis PhD will be carried out within the framework of the ANR industrial chair 'MESSIAH' (Mini-test specimens for in-service monitoring of structures with application to hydrogen transportation) in partnership with RICE-GRTgaz, EDF, Mannesmann Precision Tube, Air Liquide and Transvalor. The MESSIAH program proposes to use mini-test specimens machined from coupons extracted from facilities to evaluate and monitor the toughness during service. These in situ coupons will be small (thickness: 1-3 mm, surface area: a few cm2). The issues targeted by the project are the ageing of the installations and the taking into account of new challenges linked to the decrease of mechanical properties due to hydrogen. The interest in developing this type of methodology lies in the possibility of testing equipment already in place to evaluate their behavior under prospective conditions. Although it is relatively easy to test small tensile samples to determine the plastic behavior, the program proposes to go well beyond this objective by developing fracture mechanics tests in the ductile regime and taking into account the effect of hydrogen (the current practice being limited to brittle fracture). The main difficulty lies in the size effects.

The production of 'decarbonated' hydrogen is a way to reduce the CO2 footprint linked to human activity. This hydrogen could be produced by electrolysis of water thanks to electricity produced by photovoltaic panels, wind turbines, hydroliennes or nuclear reactors. The gas thus produced will have to be collected and transported to the consumption centers. It is envisaged to use the existing distribution networks (the construction of new networks would be very expensive). It is therefore essential to evaluate the potential effects of hydrogen on the mechanical properties of the low-alloyed steels used to manufacture the tubes. On the one hand, tests coupling mechanical stress and hydrogen loading must be conducted. On the other hand, it is also necessary to develop simulation tools to analyze these tests and eventually to better design the transport structures.

The PhD will be carried out in this context. It will focus on the implementation of tools necessary to simulate the coupling between hydrogen diffusion and mechanical behavior. These are of course constitutive equations but also finite element formulations to manage the coupling between diffusion and mechanics. An important point is the diffusion of hydrogen towards the highly stressed areas as well as its trapping. The presence of hydrogen can then affect the plastic behavior as well as the failure of materials (HELP mechanism (hydrogen-enhanced localized plasticity) for example). Within the framework of the study, we will focus on steels. All the developments will be done in the Z-set software (http://www.zset-software.com). The candidate will also have to propose a base of tests to validate the implementations.

The developments carried out in the framework of the thesis can be applied (i) to the results of the literature and (ii) to the datebase built within the MESSIAH Chair. Indeed, two other PHDs will focus on the experimental characterization of embrittlement on different materials.
ProfileEngineer and / or Master of Science - Good level of general and scientific culture. Good level of knowledge of French (B2 level in french is required) and English. (C1 level in english is required) Good analytical, synthesis, innovation and communication skills. Qualities of adaptability and creativity. Teaching skills. Motivation for research activity. Coherent professional project.

Prerequisite (specific skills for this thesis): Mechanics of solids – Constitutive relations – C++ and Python languages – Finite element simulations – Programming skills


Applicants should supply the following :
• a detailed resume
• a copy of the identity card or passport
• a covering letter explaining the applicant’s motivation for the position
• detailed exam results
• two references : the name and contact details of at least two people who could be contacted
• to provide an appreciation of the candidate
• Your notes of M1, M2
• level of English equivalent TOEIC
to be sent to recrutement_these@mat.mines-paristech.fr
FundingConvention CIFRE